%0 Journal Article
%A Gómez Alday, J.J.
%A Carrey, R.
%A Valiente, Nicolás
%A Otero, Neus
%A Soler, A.
%A Ayora, C.
%A Sanz Bas, David
%A Muñoz Martín, Alfonso
%A Castaño, S.
%A Recio, C.
%A Carnicero, A.
%A Cortijo, A.
%T Denitrification in a hypersaline lake–aquifer system (Pétrola Basin,Central Spain): The role of recent organic matter and Cretaceous organicrich sediments
%D 2014
%@ 0048-9697, ESSN: 1879-1026
%U https://hdl.handle.net/20.500.14352/34607
%X Agricultural regions in semi-arid to arid climates with associated saline wetlands are one of the most vulnerable environments to nitrate pollution. The Pétrola Basin was declared vulnerable to NO3 − pollution by the Regional Government in 1998, and the hypersaline lake was classified as a heavily modified body of water. The study assessed groundwater NO3 − through the use of multi-isotopic tracers (δ15N, δ34S, δ13C, δ18O) coupled to hydrochemistry in the aquifer connected to the eutrophic lake. Hydrogeologically, the basin shows two main flow components: regional groundwater flow from recharge areas (Zone 1) to the lake (Zone 2), and a density-driven flow from surface water to the underlying aquifer (Zone 3). In Zones 1 and 2, δ15NNO3 and δ18ONO3 suggest that NO3 − from slightly volatilized ammonium synthetic fertilizers is only partially denitrified. The natural attenuation of NO3 − can occur by heterotrophic reactions. However, autotrophic reactions cannot be ruled out. In Zone 3, the freshwater–saltwater interface (down to 12–16 m below the ground surface) is a reactive zone for NO3 − attenuation. Tritium data suggest that the absence of NO3 − in the deepest zones of the aquifer under the lake can be attributed to a regional groundwater flow with long residence time. In hypersaline lakes the geometry of the density-driven flow can play an important role in the transport of chemical species that can be related to denitrification processes.
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